If you wrote me a physical letter, it would take a few days to reach me. You put the letter in your mailbox. A postal worker picks it up. Then it travels between different post offices on its journey from you to me.

But within seconds of you sending this question over the Internet, it was sitting in my inbox. How can this be?

The whole Internet works like the mail system—but much faster. That’s what I learned from Adam Hahn, an Assistant Professor of Computer Science at Washington State University.

Everything our computers do, they do because we program them to do it. Maybe you want to design a game or an app that’s brand new. To create that game or app, you have to help your computer understand what to do.